problem with Meggy Jr
  • hello,

    I just assembled my Meggy Jr and it was working fine with the preloaded stuff both on battery and external power.
    after a while it just went blank and still it is blank. meaning does not show any sign of operation.
    my question would be where and how to start looking for possible errors or assembly failures?
    I don't have experience with hardware debugging...so any advice would be welcome.

    thanks!

    Gabor
  • I'm sorry to hear about the problem.  There are a few failure modes that would cause it to totally cease operation.

    Most obvious:  No power.   Check that the batteries (if using) are good, or that your plug-in 5 V power supply is good, and that the power jumper is installed and in the right location.  Check that there are good solder joints at the power connector/battery wires, power jumper, and at the pins of the chip.

    Also possible:  
    * Reset problem, if pin 1 of the chip or the reset button has an accidental connection
    * Clock problem, if the clock crystal or its two capacitors are not soldered well, or are cracked.
  • Thanks for your answer Windell!

    power: it seems to be ok. I measured the voltage between pin7 and pin22 and there is  power. both with battery and with power supply (which is from evilmadscientis:).
    I reheated the chip's pins to make it look better but there is no change:( still no operation.
     
    as I am beginner at the hardware debugging here comes some (stupid;) questions:
    how can I crosscheck if there is accidental connection on reset button or on pin1? I mean which points should I measure (the resistance I assume...or voltage)?
    I measured the voltage between the crystal's two pins and there is 0.15V with battery and 0.16V with 5Vpower supply when the board powered. is that ok? and how can I check the capacitors?

    I also measured voltage on the ATMEGA pins 4, 5, 6, 11, 12, 13, 14 compared to the ground and seems to be the same output(?). it is around 3.68V with battery input having 4.3V. I don't know how good it is...
    and I have only a cheap multimeter...
    there is also voltage on pins 9 and 10 (the oscillator) compared to ground. there is 0.7V with battery input of 4.3V.
    thanks for the help and patience for my amateur questions;)!

    best regards,

    Gabor


  • storno my above comments. now it is working after some work. there was a problem around the soldering of the crystal - I suspect.
    first I removed the original crystal and put a replacement there. with the replacement I uploaded one of the examples and it was working.
    but my replacement crystal was too tall - could not fit between the plastic plates - decided to remove it and put back the original one. just to see whether it was ok or I had problem with soldering. it was not working again. then I removed the original crystal at second time. but I damaged the hole in the board - there was too much heat and pulling...:( so I put two wires in the hole of the crystal and put the original crystal at the end of the wires.
    and voila - it is working....after some frustration.

    the bottom line - I should be more careful with soldering and especially more patient when removing items from the soldered place.

    thanks!

    and now the fun begins with creating games:)

    best regards,

    Gabor

  • Hmmm... Well, I'm not sure exactly what happened, but I'm glad to hear that it is working now. :)
  • I suspect that the soldering on the crystal was not perfect for the first time(?).
    one more thing I forgot to mention earlier. with my replacement crystal I tried loading a new example from the MeggyJr set. and after this attempt the board started to operate...I mean that with the replacement crystal when I switched on the board nothing has happened. only after I loaded one of the example.

    but as I wrote I don't have too much experience so I am not sure either was it soldering problem or some temporary issue with the ATmega?.